Machines, for example motor graders, are commonly used in earth leveling applications such as road maintenance or surface contouring. Motor graders typically have a steerable front frame and a driven rear frame connected to the front frame by an articulation joint. The front frame supports a movable drawbar-circle-moldboard (DCM) that holds a work implement used to perform the leveling operations. The DCM is suspended from a main beam of the front frame and has a yoke extending forward toward and pivotally connected to the front frame. Movement of the DCM relative to the front frame results in a corresponding movement of the work implement.
The work implement, typically a blade, is connected to a circle member of the DCM. The circle member is positioned relative to the yoke by way of shoes that allow relative rotation between the circle member and the yoke, but inhibit relative translation. During operation, the blade is exposed to significant forces and vibrations and, to reduce wear of the circle member and the yoke caused by operation, wear inserts made of a relatively softer sacrificial material are located between the shoes and the circle member and between the circle member and the yoke.
Over time, the softer material of the wear inserts erodes under normal conditions, and a clearance and relative movement between the shoes and the circle member and/or between the circle member and the yoke increases. This clearance and movement, if left unchecked, could result in improper positioning and/or orienting of the blade. An inaccurately positioned or oriented blade may not adequately perform an intended leveling operation.
In order to maintain desired DCM clearances, the wear inserts must be periodically adjusted and/or replaced. In some machines, maintenance of the wear inserts requires that the entire circle member and the shoes be completely removed from a bottom side of the yoke so that new wear strips and shims can be positioned between the circle member and the yoke. Although sufficient for some situations, this access to the wear inserts and performance of the associated adjustments can be difficult and require extensive time and labor.
One arrangement that allows adjustment of the wear inserts with reduced time and labor is disclosed in U.S. Pat. No. 5,720,353 (the '353 patent) issued to Wilkening on Feb. 24, 1998. Specifically, the '353 patent discloses a drawbar-circle-member having a yoke and a number of coupling assemblies secured around a periphery of a bottom plate of the yoke. Each coupling assembly includes a base, a plate-like shoe mounted to the base, and an L-shaped wear insert connected to an outwardly protruding end of the shoe. The shoe is transversely adjustable relative to the base by way of slots and one or more adjustment bolts. A circle member is axially interposed between the bottom plate of the yoke and upper portions of the wear inserts, and radially outward of end portions of the wear inserts such that the shoes axially support and radially position the circle member.
During operation of the drawbar-circle-member of the '353 patent, the upper and end portions of the L-shaped wear inserts can erode and the circle member can have space to move axially and radially relative to the yoke. Axial clearance between the yoke and circle member of the '353 patent is accommodated by adding shims to multiple top-adjust wear assemblies that protrude downward from the yoke bottom plate toward the circle member. Radial clearance between the yoke and the circle member is accommodated via the adjustment bolts and transverse movements between individual shoes and their associated bases. In this manner, the connection between the yoke and the circle member can be tightened.
Although the coupling assemblies of the '353 patent may offer reduced time and labor associated with wear insert adjustment, the assembly may still be less than optimal. In particular, the assembly still requires the wear inserts to be serviced manually on a regular basis. This manual service results in lost productivity and an operational cost of the machine.
The drawbar-circle-moldboard of the present disclosure addresses one or more of the needs set forth above and/or other problems of the prior art.